Overall 25% of the children born in Pakistan are low birth weight (LBW), defined as birth weight of less than 2500 grams. LBW is associated with increased risk of mortality, morbidity, and poor psychosocial and physical development. Known risk factors include poor maternal nutrition, low socioeconomic status, inadequate health care and smoking. About 50% of the households use wood as cooking fuel in rural and semi-rural areas of Pakistan. The relationship of indoor fuel smoke exposure to LBW has not been well studied, although the associations of cigarette smoking and air pollution to increased risk of LBW have been reported. The overall objective of the present project is to compare the incidence of LBW in neonates in a retrospective cohort of women in rural and semirural areas of southern Pakistan. We will compare LBW in infants of women who used open wood stoves for cooking during pregnancy with women who used nonsmoke producing fuel (natural gas), controlling for the potential confounding factors that may affect use of fuel as well as fetal outcomes. Both groups received routine antenatal care from the maternal and child health care program of The Aga Khan University. Birth outcomes were documented with anthropometric data within 24-48 hours of birth. A simple random probability sample of pregnant women classified by income and type of fuel used will be selected to attain the required total sample size of 766 women. A questionnaire has been developed to assess exposures and any change in exposures with time. Electrochemical monitors with a data logger (TSI, IAQ-CALCTM, Model 8762) will be used to measure CO and PM 2.5 levels in kitchens of a sample of women from each exposure group. Univariate and multivariable analyses will be done to compare LBW as primary outcome, and adverse peri-natal outcomes as a secondary outcome in the two fuel groups, adjusting for social, nutritional, reproductive, and any other confounding variables. Since use of wood is prevalent and risk of LBW is high, this study will explain a large proportion of LBW. Results will have significant implications of preventing this outcome. [unreadable] [unreadable]